This non-provisional application claims priority under 35 U.S.C. xc2xa7 119(a) on Patent Application Nos. 2001-240269 and 2001-390981 filed in Japan on Aug. 8, 2001 and Dec. 25, 2001, respectively. The entirety of each of the above applications is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a cam phase variable apparatus for varying the phase of a cam, which is driven to rotate by power of a driving rotary shaft in order to make it possible to control the operation timing of an object of operation by the cam with respect to the driving rotary shaft. More particularly, the present invention relates to a cam phase variable apparatus for varying, for example, the injection timing of a fuel injection apparatus or an opening or closing timing of an intake valve or an exhaust valve, which is operated by a cam driven to rotate by power of a crankshaft of an internal combustion engine.
2. Description of Background Art
Conventionally, one cam phase variable apparatus of the type mentioned is disclosed in the official gazette of, for example, Japanese Patent Publication No. Sho 63-30496. The cam phase variable apparatus is provided for a fuel injection apparatus of an internal combustion engine and includes a pair of helical gears having helical splines cut in the opposite directions to each other and provided on a driving shaft. A camshaft has a cam provided thereon for being driven to rotate by the driving shaft to operate a fuel control valve. Furthermore, a sleeve is held in meshing engagement with the helical gears. The sleeve is moved in an axial direction through a slip ring, which is driven to move in an axial direction by an actuator, such as an electric motor, to rotate the cam shaft and the driving shaft relative to each other to vary the phase between the cam shaft and the driving shaft. Thereby, the operation timing of the fuel control valve with respect to the driving shaft, i.e., the fuel injection timing, is varied.
Another cam phase variable apparatus as a valve timing adjustment apparatus for intake and exhaust valves of an internal combustion engine is disclosed in the official gazette of Japanese Patent Laid-Open No. Hei 11-223113. In the cam phase variable apparatus, a hydraulic chamber formed in a timing pulley driven to rotate by a crankshaft is partitioned into a delay angle hydraulic chamber and a lead angle hydraulic chamber by a vane member formed integrally with a camshaft. The vane member is rotated relative to the timing pulley by hydraulic pressure of operating oil supplied into or discharged from the delay angle hydraulic chamber and the lead angle hydraulic chamber to vary the phase of the cam shaft relative to the crankshaft. Thereby, the opening and closing timings of the intake and exhaust valves with respect to the crankshaft is varied.
Incidentally, in the cam phase variable apparatus which uses the helical gear, abrasion of the splines of the sleeve and the helical gears is liable to occur through contact between the splines when movement in an axial direction of the sleeve driven by the actuator is converted into relative rotation of the cam shaft and the driving shaft by the helical gears. Furthermore, because of play arising from the abrasion, it is difficult to keep good control accuracy of the cam phase with respect to the driving shaft over a long period of time.
In addition, in the cam phase variable apparatus, which uses the vane member driven hydraulically, it is necessary to form a hydraulic chamber or an oil path in the timing pulley and the camshaft. Furthermore, it is necessary to provide the timing pulley with a seal apparatus for keeping the operating oil in the hydraulic chamber in a high hydraulic pressure state. Thus, there is a drawback in that the timing pulley and the camshaft are very complicated in structure.
The present invention has been made in view of such a situation as described above. It is a common object of the present invention to provide a cam phase variable apparatus which can suppress the occurrence of play by abrasion at sliding portions of two rotatable members, which rotate relative to each other, to allow good accuracy in phase control to be kept over a long period of time without complicating the structure of the two rotatable members.
Furthermore, it is an object of the present invention to decrease the inertial mass of components of a cam phase variable apparatus which rotate together with a first rotatable member to suppress degradation of the responsibility of rotation of a cam to a driving rotary shaft.
Furthermore, it is an object of the present invention to achieve further augmentation of the accuracy in phase control and to achieve a further reduction in size of a cam phase variable apparatus in an axial direction.
According to a first aspect of the present invention, a cam phase variable apparatus is provided for rotating a driving side member formed from a driving rotary shaft or a rotatable member driven to rotate by power of the driving rotary shaft. A cam side member is formed from a cam driven to rotate by the power of the driving rotary shaft or a rotatable member rotated in synchronism with the cam relative to each other in order to vary the phase of the cam with respect to the driving rotary shaft. A support shaft is provided on a first rotatable member and is formed from one of the driving side member and the cam side member. A lever is supported for rocking motion around a center axial line on a plane intersecting with an axial line of rotation of the first rotatable member. A driving apparatus is provided for rocking the lever. The lever has a first operating arm for engaging with the driving apparatus and a second operating arm for engaging with a second rotatable member formed from the other of the driving side member and the cam side member. Furthermore, the lever transmits the power of the driving rotary shaft to the cam side member and provides relative rotation between the first rotatable member and the second rotatable member which commonly have the axial line of rotation when the lever is rocked by the driving apparatus.
According to the first aspect of the present invention, the phase of the cam with respect to the driving rotary shaft is varied when the lever supported for rocking motion on the first rotatable member through the support shaft and engaging at the second operating arm thereof with the second rotatable member is rocked by the driving apparatus, which engages with the first operating arm of the lever to provide relative rotation between the first rotatable member and the second rotatable member. As a result, the following effects are achieved. In particular, the lever supported for rocking motion on the support shaft can smoothly convert, through the rocking motion thereof, the driving force of the driving apparatus acting upon the first operating arm into a force acting in a direction in which the relative rotation is provided. Accordingly, the occurrence of abrasion at sliding portions on which the lever slides such as the support shaft and the engaging portion of the second rotatable member is suppressed, and good accuracy in phase control can be maintained over a long period of time. Furthermore, the relative rotation is performed through the lever, which is supported for rocking motion on the support shaft secured to the first rotatable member and engages with the engaging portion of the second rotatable member. This is different from the background art described hereinabove, wherein such relative rotation is provided making use of hydraulic pressure. Accordingly, the necessity for a seal apparatus and so forth is eliminated. Consequently, the structure of the first rotatable member and the second rotatable member can be made comparatively simple.
According to a second aspect of the present invention, the second operating arm and the second rotatable member engage with each other through contact of a spherical face of an engaging portion of one of the second operating arm and the second rotatable member with an engaging portion of the other of the second operating arm and the second rotatable member in a circumferential direction.
According to the second aspect of the present invention, the following effect is exhibited. In particular, the engagement between the second operating arm of the lever and the second rotatable member is performed through the contact in a circumferential direction between the spherical face of one of the second operating arm and the second rotatable member and the engaging portion of the other of the second operating arm and the second rotatable member. Accordingly, abrasion at the engaging portions by sliding movement is suppressed, and good accuracy in phase control can be maintained over a long period of time.
According to a third aspect of the present invention, the driving apparatus includes a first driving portion having a movable portion provided coaxially with the first rotatable member and movable in an axial direction with respect to the first rotatable member and a second driving portion having a driving force generation member for causing the movable portion to move in the axial direction. The movable portion has a transmission member movable in the axial direction and rotatable with respect to the first rotatable member and an operation member rotatable with respect to the transmission member and movable in the axial direction together with the transmission member. The transmission member is moved in the axial direction by the driving force generation member, whereas the operation member engages with the first operating arm.
According to the third aspect of the present invention, the following effects are exhibited. In particular, only the operating member, which engages with the first operating arm rotates together with the first rotatable member from among those members which compose the driving apparatus. Accordingly, the inertial mass of the components of the cam phase variable apparatus which rotate together with the first rotatable member can be reduced to suppress the degradation of the responsibility of rotation of the cam to a variation of the speed of rotation of the driving rotary shaft. Furthermore, the loss of power for driving the driving rotary shaft to rotate can be reduced. Furthermore, since the movable portion is provided coaxially with the first rotatable member, the movable portion can be disposed compactly in a diametrical direction of the first rotatable member.
According to a fourth aspect of the present invention, a driven member, which rotates together with the transmission member and to which the rotational driving force from the driving force generation member is transmitted, is provided on the transmission member formed from a cylindrical member. A threaded portion for meshing with a threaded portion provided at a fixed portion of the first driving portion to move the transmission member in the axial direction upon rotation of the transmission member is formed on a circumferential face of the transmission member.
According to the fourth aspect of the present invention, the following effect is exhibited. In particular, the transmission member rotated by the rotating driving force transmitted from the driving force generation member through the driven member has the threaded portion which meshes with the threaded portion of the fixed portion. Accordingly, a reactive force and an assisting force acting upon the cam from the member driven by the cam and transmitted to the movable portion are intercepted by the threaded portions and do not act upon the driving force generation member. Consequently, occurrence of an increase or decrease of the control load acting upon the driving force generation member is prevented and degradation of the accuracy in phase control is prevented.
According to a fifth aspect of the present invention, the support shaft is positioned in an internal space of the transmission member and disposed such that the support shaft and the transmission member overlap with each other as seen from the direction perpendicular to the axial direction.
According to the fifth aspect of the present invention, the following effects are exhibited. In particular, the support shaft is disposed making use of the inner space of the cylindrical transmission member inwardly of the transmission member. Accordingly, an increase in size of the movable portion and hence of the cam phase variable apparatus in a diametrical direction can be suppressed. Furthermore, since the support shaft and the transmission member are disposed such that they overlap with each other as seen from the direction perpendicular to the axial direction, the movable portion and hence the cam phase variable apparatus can be miniaturized in the axial direction.
According to a sixth aspect of the present invention, a stroke sensor for detecting an amount of movement of the movable portion in the axial direction is provided, and a control apparatus for controlling the driving force generation member based on a detection signal of the stroke sensor is provided.
According to the sixth aspect of the present invention, the following effect is exhibited. In particular, the operation member of the movable portion, which moves in the axial direction, rocks the lever to provide relative rotation between the first rotatable member and the second rotatable member. Accordingly, a phase variation amount of the cam is detected by the stroke sensor. Then, since the control apparatus controls the driving force generation member based on a result of the detection, the accuracy in phase control can be augmented.
According to a seventh aspect of the present invention, the driving force generation member is an electric motor. The electric motor is disposed such that a rotary axis thereof and the first rotary member extend in parallel to each other and overlap with each other as seen from the direction perpendicular to the axial direction.
According to the seventh aspect of the present invention, the following effect is exhibited in addition to the effects of the invention as set forth in the claims referred to. In particular, since the electric motor is disposed such that the rotary shaft thereof extends in parallel to and overlaps as seen from the direction perpendicular to the axial direction with the first rotatable member, the cam phase variable apparatus can be miniaturized in the axial direction.
It should be noted that, in the present specification, an axial direction signifies the direction of an axial line of rotation of a first rotatable member (in the embodiments, for example, an outer shaft or a camshaft). A diametrical direction and a circumferential direction signify a diametrical direction and a circumferential direction of the first rotatable member, respectively.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.